Pyrosequencing analysis of the microbiota of honeybee products and honeybees revealed the predominance of Lactobacillus kunkeei in honey, bee pollen, bee bread, and royal jelly. L. kunkeei was isolated from bee pollen, bee bread, and honey stomach, and its effect on IgA production was evaluated in vitro. Heat-killed YB38 and YB83 isolates from bee pollen promoted IgA production in mouse Peyer's Patch cells and had little mitogenic activity or effect on IL-2 production in mouse spleen cells in comparison with Listeria monocytogenes, which does exhibit mitogen activity. A pilot study in 11 healthy adults showed that 4-week intake of 1,000 mg/day heat-killed YB38 increased SIgA concentrations and secretion in saliva with no adverse effects.